The Jim Conforti chip has the best reputation from what I've seen in this board, but owning a 1988 528e I cannot say for sure, since no chips exist for this particular model. If I understand correctly, these cars have their ignition map retarded sufficiently to run smoothly with low octane gas. The chips simply advance the ignition such that you have to use premium fuel. You get quite a few hp's as well from a slight redline increase. If I had a 82-87 eta I'd get one for sure.